The invention generally relates to methods for modifying the surfaces of elastic substrates.
It has now been established that the surface properties of materials (i.e., wetting, lubrication) can be successfully tailored by terminally attaching various organic modifiers. In particular, the deposition of self-assembled monolayers (SAMs) may offer one of the highest quality routes used to prepare chemically and structurally well-defined surfaces (A. Ulman, An Introduction to Ultrathin Organic Films from Langmuir-Blodgett to Self Assembly (Academic Press: New York, 1991); M. Chaudhury, Mat. Sci. Eng. Rep. 16, 97 (1996)).
One of the crucial issues concerning the application of SAMs is the knowledge of molecular level organization of the SAM chains. The wetting properties of SAMs and their stability are believed to be governed by the intimate interplay between the chemical nature of the terminus of the monolayer molecule (xcfx89-) and the packing within the SAM. The surface properties of the SAMs can range from hydrophobic to hydrophilic. The SAM packing in turn is believed to influences the two-dimensional arrangement of the xcfx89-functionalized surface groups. For example, it is believed that the degree of packing of the SAMs not only determines the surface energies of the SAMs, but ultimately influences the stability of the monolayer and its resistance against surface reconstruction (J. Wang, G. Mao, C. K. Ober, and E. J. Kramer, Macromolecules 30, 1906 (1997)). While the xcfx89-character is fixed by the chemical structure of the terminal group, the packing can be altered by varying the density of the grafting points at the surface. However, tailoring the grafting density of the SAM chains is typically not an easy task. Almost all SAMs are formed via natural self-assembly processes that are usually governed by the chemical and structural nature of the SAM molecules and the means of their attachment to the solid surface. However, when combined with mechanical manipulation, the grafting density and thus the chain packing can be altered.
In one aspect, the invention provides a method of depositing a functional group on a surface portion of an elastic substrate. The method comprises the steps of stretching an elastic substrate having an initial surface portion to form an enlarged surface portion from the initial surface portion, then conjugating a functional group on the enlarged surface portion, and then releasing the substrate to form a reduced surface portion from the enlarged surface portion. The reduced surface portion has an area less than the enlarged surface portion, and with the reduced surface portion having the functional group deposited therein at a greater density than the enlarged surface portion.
These and other aspects and advantages of the invention are described in greater detail herein.